2018-03-20T07:32:06Zhttp://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=3392016-12-0110.24200Scientia IranicaScientia Iranica1026-30981026-30982016236Nonlinear free and forced vibrations of curved single walled carbon nanotube on a Pasternak elastic foundationMehdiAkbarzadehA.FarshidianfarMasoudTahaniBased on elastic continuum mechanics, the nonlinear free and force vibrational analysis of an embedded single walled carbon nanotube (SWCNT) with waviness along its axis is analyzed. The single-walled carbon nanotube embeds in a Pasternak elastic foundation. Two analytical approaches utilize to obtain the frequency-amplitude relationship of the free vibrational model, and another analytical approach propose to obtain the forced vibrations of the curved single walled carbon nanotube on the Pasternak elastic foundation. Subsequently, a parametric study is performed to study the importance of different parameters, such as the amplitude of oscillation and the curvature radius, on the nonlinear behavior of the system. Finally, numerical simulation is carried out to obtain the results and investigate the accuracy of the analytical solution methods. Comparison of the results obtained by proposed methods show excellent agreement with those obtained by numerical solution.Curved carbon nanotubeNonlinear vibrationVariational approachHamiltonian approachPerturbation theory2016120130873098http://scientiairanica.sharif.edu/article_4014_d5efd346ce363a6103dfed515a117cac.pdf2016-12-0110.24200Scientia IranicaScientia Iranica1026-30981026-30982016236Nonlocal nonlinear first-order shear deformable beam model for postbuckling analysis of magneto-electro-thermo elastic nanobeamsR.AnsariR.GholamiIn this study, the size-dependent postbuckling behavior of magneto-electro-thermo-elastic (METE) nanobeams with different edge supports is investigated. Based on the nonlocal first-order shear deformation beam theory and considering the von Kármán hypothesis, a size-dependent nonlinear METE nanobeam model is developed, in which the effects of small scale parameter and thermo-electro-magnetic-mechanical loadings are incorporated. A numerical solution procedure based on the generalized differential quadrature (GDQ) and pseudo arc-length continuation methods is utilized to describe the size-dependent postbuckling behavior of METE nanobeams under various boundary conditions. The effects of different parameters such as nonlocal parameter, external electric voltage, external magnetic potential and temperature rise on the postbuckling path of METE nanobeams are explored. The results indicate that increasing the non-dimensional nonlocal parameter, imposed positive voltage, negative magnetic potential and temperature rise decrease the critical buckling load and post-buckling load-carrying capacity of METE nanobeams, whilean increase in the negative voltage, positive magnetic potential lead to a considerable increase of critical buckling load as well as postbuckling strength of the METE nanobeams.Firs-order shear deformable nanobeamMagneto-electro-thermo-elastic materialsPostbucklingNonlocal elasticity theorySmall-scale effect2016120130993114http://scientiairanica.sharif.edu/article_4015_f7e67471deeedbf11ea0eff17312d8dc.pdf2016-12-0110.24200Scientia IranicaScientia Iranica1026-30981026-30982016236Output power enhancement of Rh6G dye laser by colloidal gold nanoparticlesAhmadMoshaiiImprovement of the efficiency of a Rh6G dye laser by adding proper concentrations of gold colloidal nanoparticles into the dye solution has experimentally been investigated. Gold colloidal nanoparticles due to their strong plasmonic peak in the visible region are expected to have a considerable interaction with Rh6G dye molecules with broad emission spectrum in the visible range. It is shown that with addition of enough low concentrations (less than 0.4 µM/l) of gold nanoparticles to the dye solution, both the output power and the efficiency of the dye laser increase. The best improvement of the laser efficiency reaches 15%. Two amplifying mechanisms exist for efficiency improvement by the nanoparticles, which are resonant energy transfer from the plasmonic nanoparticles to the dye molecules in addition to the high near field around the nanoparticles. The results indicate that in the low concentrations of gold nanoparticles, the amplifying mechanisms dominate the dissipating mechanism of scattering of the pumped light by the nanoparticles. This leads to the efficiency improvement by addition of the nanoparticles.Gold colloidal nanoparticlesRh6G Dye laserPlasmonicPower enhancement2016120131153122http://scientiairanica.sharif.edu/article_4016_463d89f363f219d58f8491b1271aa245.pdf2016-12-0110.24200Scientia IranicaScientia Iranica1026-30981026-30982016236The effect of Carbon Nanotubes/Bioglass nanocomposite on Mechanical and Bioactivity properties of Glass Ionomer CementMohammad RezaForoughiMaryamKhoroushiReyhanehNazemElhamAkbarian TefaghiThe aim of this study was to manufacture and characterize Carbon Nanotubes (CNTs)/bioglass (BG) to improve the mechanical and biocompatibility properties of Glass-Ionomer Cement (GIC). The powder of Glass-Ionomer Cements was prepared through fusion and carbon nanotubes and bioactive glass were manufactured through fusion and added to the cement to improve its mechanical and bioactive properties. To evaluate the biological adaptation of manufactured composites, they were placed in simulated body fluid (SBF). Finally, the compressive strength test and erosion test showed that the mechanical properties of Glass-Ionomer Cement are two folds of those when 1% carbon nanotubes are used (PNanocompositesGlass ceramicsGlass Ionomer CementCarbon NanotubesBioglass 45S52016120131233134http://scientiairanica.sharif.edu/article_4017_cf27abe512e2705d491d2fd5f14b3ac3.pdf2016-12-0110.24200Scientia IranicaScientia Iranica1026-30981026-30982016236Fabrication and study of UV-shielding and photocatalytic performance of uniform TiO2/SiO2 core-shell nanofibers via single-nozzle co-electrospinning and interface sol–gel reactionOmolfajrNakhaeiNasserShahtahmassebiMahmoodRezaee RoknabadiMohammadBehdaniOne-dimensional TiO2/SiO2 core-shell nanofibers were fabricated using a single-nozzle co-electrospinning process with phase-separated, mixed polymer composite solution. The core and shell are composed of Polyvinylpyrrolidone (PVP) and Polyacrylonitrile (PAN) polymers with uniform distribution of TiO2 and SiO2 nanoparticles (NPs), respectively. The NPs were synthesized via sol-gel reaction, simultaneously, in the respective polymer solutions. The morphologies and structures of the fabricated TiO2/SiO2 core-shell nanofibers were investigated by XRD, FTIR, SEM, EDS and TEM images. The influence of different amounts of TiO2 and SiO2 precursors on the photocatalytic and UV-shielding performance of TiO2/SiO2 core-shell nanofibers were studied. Photocatalytic activity of the nanofibers evaluated by observing photodegradation of Methyl Orange (MO) aqueous solution under irradiation of ultraviolet (UV) light. Our results on the TiO2/SiO2 core-shell nanofibers indicate good potential for superior applications in photocatalytic and UV shielding devices.NanofibersCore-shell structuresElectrospinning method UV-shieldingphotocatalytic performance2016120131353144http://scientiairanica.sharif.edu/article_4018_cfc144ce48a37dc3f8cf477f73a530d3.pdf2016-12-0110.24200Scientia IranicaScientia Iranica1026-30981026-30982016236Effect of Multi-wall Carbon Nanotubes(MWNTs) on Structural and Mechanical Properties of Poly(3-hydroxybutirate) Electrospun Scaffolds for Tissue Engineering ApplicationsSaeedKarbasiMoeinZareiMohammad RezaForoughiThe aim of this study was to improve the electrospinning parameters and evaluate the effects of Multi-Walled Carbon Nano-Tubes (MWNTs) on the structural and mechanical properties of Poly-3-hydroxybutyrate (P3HB) electrospun scaffolds. To this end, to achieve optimal properties of the electrospinning machine, P3HB polymer solutions were prepared at different concentrations and spinned. After optimization, MWNTs at different weight percentages (0.5%, 0.75%, 1% and 1.25%) were added to the polymer solutions and electrospinned. The effects of different concentrations of MWNTs on the structure of fibers and properties of the scaffolds were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) techniques. Evaluation of the scaffold morphology showed the presence of MWNTs into fibers, that Adding different amounts of nanotubes increased the average diameter of the fibers,with the mean increase reaching 700 nm from 240 nm. In addition, evaluation of porosity with the use of SEM photomicrographs and the MATLAB software program showed an increase in porosity from 81% to 84% in the presence of MWNTs. The analysis of mechanical properties of the PLGA/MWNTs composites revealed 158% improvement over pure PHB scaffold, So that the tensile strength in presence of only 0.5% MWNTs increased from 2 to 5.15 MPa. According to mechanical and structural properties obtained, the best amount of MWNTs was 0.5 wt%. Therefore, it is possible to significantly improve the structural and mechanical properties of pure P3HB scaffolds by incorporating some MWNTs to their structure so that they can become favorable for tissue engineering applications.Nano-composite scaffoldspolyhydroxy butyratemulti-walled carbon nano-tubesElectrospinningTissue Engineering2016120131453152http://scientiairanica.sharif.edu/article_4019_1cf7808f33efb18ee64c4c4c27cfaa21.pdf2016-12-0110.24200Scientia IranicaScientia Iranica1026-30981026-30982016236Impact dynamics of metallic nano particles in collision with graphene nano sheetsSadeghSadeghzadehIn this paper impact of metallic nanoparticles on graphene sheets was investigated via non equilibrium molecular dynamics (NEMD) approach. Upon unique feature of graphene to absorb motion energy of the materials impacted on it, systems based on graphene can be an appropriate solution for the purpose of damping. The proposed model was validated by available experimental data and simulation. It was demonstrated that mechanics of impact is not a multidimensional problem, therefore it can be studied by molecular dynamics. Effect of velocity of the particles, impact angle and number of the graphene sheets on the coefficient of restitution of the metallic nanoparticles was researched. Contrarily to macro systems, it was observed by increasing the velocity of impact, coefficient of restitution decreased. Also by increasing impact angle, coefficient of restitution changed with the formula: e(theta)=0.418(theta)^2-0.045(theta)-0.396. By increasing the graphene sheets, the coefficient reduced significantly. Negative coefficient of restitution was observed for some cases, which was reported also on other works about nanostructures. It was shown a single graphene layer can withstand 3.64 times more than a 20 layer graphene sheet toward impacting.Single Layer Graphene Sheet (SLG)Few layer Graphene Sheets (FLGS)Coefficient of RestitutionCoefficient of reboundCollision2016120131533162http://scientiairanica.sharif.edu/article_4020_85ff065a6daf010cdca7ec0acfc9d466.pdf2016-12-0110.24200Scientia IranicaScientia Iranica1026-30981026-30982016236Facile Template-less Fabrication of ZnO Nanostructures;On the Consideration of Several ParametersSamanehGhasabanMohammadAtaiMohammadImaniAliakbarTarlaniZnO nanostructures were formed via a hydrothermal reaction mechanism between simple anionic (ammonia orsodium hydroxide) and cationic (zinc acetate dehydrate) precursors without using any organic templates. Effect of the reaction conditions including the initial solution pH, concentration and type of the anionic and cationic precursors, and the reaction time and temperature on the nanostructure particle size and morphology were investigated. The nanostructures formed were analyzed by powder X-ray diffraction, energy dispersive X-ray analysis, and scanning electron microscopy. According to the results, the morphology of the nanostructures is highly pH-dependent. Needle-like nanostructures were formed using ammonia at initial solution pH value around 9 but plate-like nanostructures were formed using NaOH at pH value around 13 regardless of the reaction time or temperature. Varying the precursor concentrations could not be considered as an independent parameter per se due to the consequent changes impress the reaction medium pH which affects morphologies in turn. In general, increasing the reaction time and temperature increased the mean particle size of the nanostructures with no significant change in their morphology. It was found that the nanostructure morphology changes from nanoneedles to star-like ones due to higher addition rate of ammonia.Hydrothermal reactionZinc oxideNanostructuresmorphology2016120131633174http://scientiairanica.sharif.edu/article_4021_5db9e99c66649663d45a77a40eabcf48.pdf